Common-rail injection systems, which operate with very high injection pressures, are being used increasingly in fuel supply systems of internal combustion engines. In these common-rail injection systems, fuel is pumped by a high-pressure pump into a high-pressure reservoir, from where the fuel is injected into the combustion chamber of the internal combustion engine using fuel injectors. Injection valves are provided for injecting the fuel. These normally have an admission connector, via which the fuel is admitted under pressure. A specified amount of fuel, controlled by a control device, is injected into a cylinder of an internal combustion engine. The high injection pressure means that not all of the admitted fuel is injected into the cylinder. Hence the excess fuel that is not injected must be taken away from the injection valve. This is normally done via a backflow connector on the injection valve.
The backflow connector on the fuel injector generally also has a connector nipple on which the backflow pipe is mounted. In order to prevent the connector nipple being forced out by the fuel flowing out of the fuel injector, the connector nipple must be secured on the fuel injector. EP 0886065A1, for example, discloses such a backflow connector for attaching a backflow pipe to a fuel injector. This backflow connector, also called backflow nipple below because of its preferred shape, includes a U-shaped fastener whose arms are undulatory in shape, where the fastener can be inserted into lateral slots on an end connector element. It thereby engages in a securing position in an annular groove on an insert of a connector nipple, which is inserted into the end connector element.
DE 19900508C2 describes a backflow connector for attaching a backflow pipe to a fuel injector, which has an end connector element that is constructed as a single piece with the injector body. A connector nipple engages by its insert in a hole in the end connector element. An axial securing device in the form of a pre-tensioned clip having a recess on each arm in the end connector element is arranged substantially at right angles to the connector nipple.
It is essential to ensure that no mistakes are made when fitting the end connector element and the securing element.